1. Field
Embodiments of the disclosure relate generally to the field of fan air modulation for aircraft environmental control precooler systems and more particularly to an air modulating valve for a precooler with dual doors for flow redirection activated for mirrored rotation by a single actuator.
2. Background
Large commercial aircraft employ environmental control system (ECS) for cabin air pressure and temperature that rely on bleed air from the engine compressor section. In aircraft with turbofan engines the compressor bleed air is cooled by a heat exchanger—termed a precooler—with diverted fan bypass air flow and is then routed to the ECS system and any other systems that use the bleed air. In the case of tight (constrained) engine installations, the exhaust from the precooler can be very close to other hardware such as engine accessories, aft mount for the engine or structure of the strut. The proximity of the precooler exhaust, which may operate at some fairly high Mach number flows, to the aft mount for the engine can also generate undesirably high pressure losses. These pressure losses may be detrimental to the precooler performance and to the design optimization of the ECS system, especially for modern, higher-bypass-ratio turbofans, where the supply pressure of the fan bypass is lower than earlier turbofans. Prior art systems employ a combination of a fan air modulation valve upstream of the precooler for flow regulation and fixed position louvers mounted on the aft face of the precooler to divert the flow.
It is therefore desirable to provide to provide a higher efficiency system for control of the fan bypass air flow by reducing the pressure losses from the heat exchanger exhaust flow and also to control the direction and pattern of the exhaust flow.